Material pressure foot for sewing machines

ABSTRACT

A pivotally mounted apron or sole for applying pressure to a material being sewed is provided with locking means which temporarily locks the apron in substantially horizontal position until the initial edge of the material-to-be-sewed has passed beyond the needle in order to prevent partial or total blocking of the edge of the material by a slanted sole. Once the material to be sewn passes a predetermined point, the locking means is released so that the pivotable apron operates in its normal desirable way.

[ 1 MATERIAL PRESSURE FOOT FOR SEWING MACHINES [75 Inventor: EugenAngele, Kaiserslaute'rnllfalz,

Germany [73] Assignee: Pfaff Industriemaschinen GmbII,

Kaiserslautem/Pfalz, Germany 221 Filed: June 13, 1972 211 App]. N6;262,188

[30] Foreign Application Priority'Data Mar. 10, 1972 Germany P 21 30719.7

52 U. S.Cl. a ...112/235 51 1111. C1. D051) 29/02 58 Field 61 Search112/235, 237,-23s, 112/236, 239, 1 50, 151, 240

[5 6] References Cited UNITED STATES PATENTS 2,147,128 2/1939 Sailer112/235 Dec. 4, 1973 2,419,482 4/1947 Clayton 112/235 1 2,481,175 9/1949Tamburro.... 112/235 3,511,198 5/1970 Hacking 112/235 FOREIGN PATENTS ORAPPLICATIONS I 186,026 7/1960 Sweden .1 11 2/235 Primary Examiner-JordanFranklin Assistant Examiner-Peter Nerbun Attorney-Greene & Durr 1 [57]ABSTRACT locking means is released so that the pivotable apron operatesin its normal desirable way.

3 Claims, 2 Drawing Figures 1 MATERIAL PRESSURE FOOT- FOR SEWINGMACHINES goods being sewed over its entire. bottom surface;

Where the center of rotation of the material pressure foot. apronremains generally behind the stitch forming place, the apron takeson-wh'em the material edge at the start of sewing: rests in front ofthe. center of rotation: a sloping position andthereby braces.itselfwedgeshaped against the edge of thematerial; The materialtransport at the start of the seam is then rendered difficult or failscompletely with bulky-goods.Thentthematerial feed seizes the goods--with' only .a small portion of the teeth and high-pressuremust beapplied against the slopingupright apron to overcomethe resistance ofits spring pressure. Thereby, stitch accummulationor damage to thematerial by the forwarding. mechanism of the sewing machineresults.Withithis invention,

these drawbacks are avoided with: the aid o'fa single' means.

To that end, the invention is based on the technical problems ofestablishing the pressurefoot sole in an essentially horizontalposition, while, atthe beginning of.

sewing, until there is an adequate transferofia sufficient amount ofsewing goods under it.

According to the invention, this problem is solved by providingcooperating locking and unlocking means between the carrier and thepressure foot-sole, con.

structed and arranged so that the. locking meanslocksthe apron in anessentially horizontal position at the be: ginning of thesewingprocess'and the unlocking means automatically unlocks thelockduringthesewing process. Thereby the stitching can be starteddirectly at the edge of the goods to be sewed, during which the bottomcomprises a bar fastened thereon, a swivally mounted locking element onthe carrier with a notched surface.

of a design for holding the bar and a springfor assuring the connectionbetween the bar and thenotched surface. v

For assuring insertion of the lockingv element, the notched surfaceincludes a leading surface for the-bar which limits the swivel range ofthe-bar.

In order that the pressure foot sole doesnot tip.with-- its headdownward upon lifting. the material pressure foot, a pressure spring isarranged normally behind the coupling axis between thecanier-andfltheusole; This pressure spring is also advantageously-usedto guarantee the locking position of the bar.

In order to attain a completely automatic. in and outconnection of thelocking mechanism-during. the sewing operation, a-spring presses thelocking element towards the disconnected direction-"towardsa stop and. acasing-mounted stop projects in the motion path'of a sloping surfaceprovided at the upper end of the .lock-.

ing element for the switching in of the locking means.

ln this'case, it is necessary that the position of the bar in: relationto the lower side of the sole be so chosen that the sole in thelockedpositiontakes a slightly; rising sloping: position inthe directionof itstop and moreover the unlocking stroke of the lock is determined in. sucha way that it releases the locking bar in-the straighthorizontalpositionof the sole. Theswitching in of the lock elements forthe securing of the sole results automatically fromthe withdrawal of thematerial pressure foot at the end of a seam. v

The invention is especially advantageous when arranged in combination.with a material feed which by its lifting movement above the needleplate takes on a slight rising,sloping position. in. the direction; ofthe sup.- port, in which= the unlocking stroke of the lock connection:between. the bar and the notches surface is chosen smaller than theamount of the-sewing of the bar (about its horizontal-axis) from itshorizontal position to its sloping position as produced by materialfeed. The apron can. then be locked. exactly in horizontal positionwhereby its optimal transport relation is provided; for starting the.sewing. The unlocking; of the lock results immediately after the edge ofthe sewing goods is pushed, forward to behind the center of rotation ofthe pressure foot sole, provided the shape regulated material feedswings the sole sofar that the bar is lifted from the notched surface ofthe locking element.

A practical example of the invention is shown in the drawing, and will.be more precisely described below.

In the drawing:

Fl G.-1 is a partial side view of a sewing machine with locked lockingmeans of the. pressure foot apron or sole.

In the casing. 1 of the machine, the needle rod 3 equipped :with. theneedle 2 is supported and is, in known way (not shown), driven throughconnecting rod 4. .Also, material pressure rod Sis slidably supported inbushing 6-in casing lQThe lower end of material. pressure-rod S- carriesa material pressure foot 7, while on the:upper end, abovea sphere 8,there is impressed a leaf spring 9 attached in known way to the casing.Through a cup-like depression in the material pressure rod 5 and. in theleaf spring 9, the position of the sphere 8 is fixed.-

On the material pressure rod 5, a lifter 10 is attached, whose arm 11 isguided in a vertical slot 12 in the casing 1.

A shaft 13 is supported in the casing l, which on its inner end carriesan eccentrically mounted lug l4 and Y to a portion of which, eittendingoutside the housing, is attached a hand lever "15. A pivot piece 16, inthe line of sight (as shown) issupported in casing 1, behind slotl2f-and has its lower impact face 17 resting on lug 14 while its upperimpact surface extends below arm 1 1. The material pressure foot 7 showsa carrier 19 which is screwed onto material pressure rod 5. On the lowerpart of the carrier 19 is the pressure foot sole or apron 20 pivotallysupported by means of a linking pin 21, the. pivotability thereof beinglimited through stop faces 22.

and 23. Between the surfaces 23 and the sole 20, a

pressure spring 24 is arranged.

On the carrier 19 an arm 25 is developed, on which is pivotallysupported a locking element 27 bymeans of a hinge pin 26. The lockingelement 27 shows a notch which is defined by a leading surface 28, adetent and a stop surface 29. The lead surface 28 and the stop surface29 can determine the range of pivotability of the pressure foot sole 20,taking over from the stop surfaces 22 and 23, which is a technicaladvantage considering the large interval of the linking pin 21. Theleading edge 28 changes over into an undercut or detent surface 30 (FIG.2) for a holding lug such as bar 31 which stretches between two forkedarms 32 extending to the rear of sole 20. The pressure produced byspring 24 provides a sufficiently strong friction bond for the bar 31 inthe outline surface 30. The detent surface can be further cut away toincrease the attachment.

Torsion spring 33 supported around the hinge pin 26 with one end thereoffixed in arm 25, and the other end pressing the locking element 27,urges the locking element 27 towards its release off of the barattachment to its limited ofi-position against the'edge 34 of carrier 19(see FIG. 2). The inclined surface 35 formed on a lock element 27cooperates with lug 36 which is formed as the end of a right-angle bentarm 37 which in turn is fastened to an adjustably carried holder 38 ofsleeve 6. i

The material pressure sole 20 cooperates with the material feed orpusher 40, which executes a so-called skip movement and forms part ofthe usual feed movement, to displace the sewing goods 39..Thematerialfeed 40 projects through slit 4] of needleplate 42 and iscarried on the material forwarding rod 43. The latter has one endpivotally connected by hinge pin 44 to crank 45 which is fastened to aslide motion translating shaft 46, while its other end is engaged tolink guide 48 through hinge pin 47, which is pivotally mounted to crankarm 49. The latter is attached to lift shaft 50 which translates thelifting movement for material pusher 40.

With the execution of the vibratory motion of lift shaft 50, the crankarm 49 lifts and lowers the end of material forwarding rod 43 throughlink 48 and pivot pin 47 so that rod 43 and the material feed 40receives a vertical swing movement in addition to its horizontalmovement imparted by shaft 46 and pivot pin 44.

So that a safer transport is guaranteed, it is necessary that the teethof the feed 40 slant to the left as shown in the drawing to engage thesewing goods during its entire stroke above the stitch plate 42. Thismeans that the material feed 40 directly after its passage through thestitch plate 42 passes parallel to the latter, and in its highestposition as a result of the described impulses of material forwardingrod 43, will receive a slight tilt- By the'further lifting of the shaft5, the inclined surface 35 of lock element 27 bears against lug 36 sothat the lock element pivots against the force of spring 33. Thereby,the guide surface 28 passes under rod 31 and leads the latter to detentsurface 30. There, under the operation of spring24 and the resultingfriction be tween bar 31 and the undercut surface, thes'ole is retainedand held with its lower side parallel to the needle plate 42. The forceof torsion spring 33 is so chosen that it does not overcome the frictionbetween the undercut surface 30 of the lock element and the bar 31.

The sewing goods 39 can now be placed under the sole 20 and the materialpressure foot 7 can be lowered back in known way by reversing the handlever 15. When the seam is started on the material edge 51, the lattermust, by the beginning of the sewing, lie under pressure foot 7, asshown in FIG. 2. The pressure of leaf spring 9 operates through materialpressure rod 5 on sole 20. The force will be transmitted by linking pin21 to sole 20. In this way, a torque onthe pressure foot sole 20develops around the edge 51 laying below needle 2 in the position shownin FIG. 1. A corresponding edge movement of the sole 20 is howeverprevented by the latch mechanism of lock element 27 and bar 31. Thereby,the sewing goods is pushed forward in the normal way through materialpusher 40 and need not be pushed forward against an already slantinglyadjusted sole 20.

As soon as the edge 51 of material 39 is forwarded past the sewing axis21 of the sole 20, it escapes from the action of the torque movement ofFIG. 1 by virtue of the parallel sewing goods on the sole. The sole 20is supported no longer through bar 31 on the surface 30 but ratheraligns itself, when the sewing goods 39 no longer lies on one side ofthe sole 20, parallel to the stitch plate 42 or parallel to the materialfeed 40.

The slight swing of the sole 20 to a position parallel to the needleplate 42 or parallel to the material feed 40 lifts bar 31 off of surface30, so that the locking element 27 moves under the action of torsionspring 33 against the edge bearing 34.

The pressure foot sole or apron conforms now to a normal, hingesupported, construction with its known advantages for sewing goodshaving an irregular upper surface.

When the needleplate 42 provides the loosening means for the lockingmechanism between carrier 19 and sole 20, the measurements between thenotched surface 30 and bar 31 are so chosen that the lower side of sole20 in locked position, receives a minimal rising tilt against the tip ofthe sole and the bar- 31 releases the ing rising in the feed direction.In this way, the sewing goods by transport through the forwarding teethof material feed 40, will not be pushed together but will be faultlesslytransported.

The material pressure foot 7 is raised by horizontally swinging the handlever 15, which through the shaft 13, the eccentric lug 14, and pivotpiece 16 causes surface 18 to engage arm 11 of lifter 10 to lift rod 5and foot 7. The lifter 10 can besides cooperate in known manner (notshown) with a lifting device which is set in motion by an operatorsknee.

As soon as the material pressure sole is lifted from the sewing goods orfrom the needle plate, the sole lays against the stop edge 22 under theoperation of spring 24.

locking element 27 in the 20.

When the material feed 40 provides the loosening means for the lockingmechanism between the carrier 19 and the sole 20, the measurementsbetween the notches surface 30 and the bar 31 are so chosen that theunderside of the sole 20 will be maintained stationary in exactlyhorizontal position. i

The latter way yields an optimal transport relationship with the startof the sewing. In this case, the locking mechanism of lock element 27 isloosened as a result of the horizontal swing of the sole 20 which isproduced through the tilting of the material feed 40 in its highestposition of its power drive movement.

I claim:

horizontal position of the sole l. A material pressure foot for a sewingmachine of the type having a reciprocating needle sewing means, a needleplate with a slot therein below the pressure foot, which plate supportsthe material to be sewed, and a material feed means constructed tointermittently move upwardly and rearwardly through the slot in theneedle plate to press the material to be sewed against the pressure footand move said material away from the needle sewing means as it is sewed,the improved construction wherein said pressure foot comprises a carrierand a pressure foot sole hinged to the carrier through an axlepositioned behind the needle sewing means,

a first spring means arranged behind the axle which connects thepressure foot sole to the carrier and normally pivotally urges theforward part of the pressure foot sole upwardly,

a locking element pivotally mounted on said carrier and having a lowerportion projecting into the path of the rear portion of said sole,

said sole having bar means at the rear end thereof adapted to cooperatewith said locking element,

said locking element haivng stop surfaces which, in a first positionthereof, cooperate with said bar means to limit the pivotal movement ofsaid'sole about its axle, second spring means mounted on said carrierand normally urging said locking element toward its first position,

said stop surfaces of said locking element including in addition anotched surface which, when said locking element is in a second positionthereof, when said presser foot is raised at the beginning of a sewingoperation, interlocks said locking element with the bar means andcooperates with the first ment to the forwarding rod and itsmaterial-feed device,

and second spring means to hold the sole substan-' tially parallel tothe needle plate as material to be sewed is introduced into the machineand to be released from said bar when said material to be sewed istransported beyond the pivoting axle of the sole by the material feedmeans. 2. The material pressure foot as claimed in claim 1, comprisinglifting means adapted to lift the carrier and pressure foot sole,

said locking element having a portion extending above the pivotalmounting on said carrier, said portion ending in a slanting surface,stationary means positioned in the path of said slanting surface wherebyupon lifting the carrier and pressure foot the locking element is movedagainst the action of the second spring to its second position to lockthe sole in its intermediate position. 3. The material pressure foot asclaimed in claim 1 in combination with a material-feed means constructedso as to cooperate with the material pressure sole, said material feedmeans comprising arelatively long forwarding rod extending under thestitch plate, the material feed device having teeth for engaging thematerial i being sewed being carried by the forwarding rod, a slidemotion translating shaft linked to one end of the forwarding rod toimpart a horizontal oscillating movethe other end of said forwarding rodbeing linked to a vibratory lift shaft, said material feed rod andshafts being so constructed that the path of the teeth of the materialfeed move substantially parallel to the stitch plate when extendingthrough the slot in said stitch plate.

, UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3.776.159 neeember .4, 1913 Inventor Euqen Anqe 1e It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the title page, in the line following "(3o) Foreign ApplicationPriority Data", the date "Mar. 10,

1972" should read June 21, 1971 Signed anci sealed this 16th day of July1974.

(SEAL) Attest:

McCOY M. GIBSON, JR. I c. MARSHALL DANN Attesting Officer Commissionerof Patents FORM PO-1050 (10-6 uscoMM-Dc 60376-P69 I v 9 U.S. GOVERNMENTPRINTING OFFICE I969 0366-334

1. A material pressure foot for a sewing machine of the type having areciprocating needle sewing means, a needle plate with a slot thereinbelow the pressure foot, which plate supports the material to be sewed,and a material feed means constructed to intermittently move upwardlyand rearwardly through the slot in the needle plate to press thematerial to be sewed against the pressure foot and move said materialaway from the needle sewing means as it is sewed, the improvedconstruction wherein said pressure foot comprises a carrier and apressure foot sole hinged to the carrier through an axle positionedbehind the needle sewing means, a first spring means arranged behind theaxle which connects the pressure foot sole to the carrier and normallypivotally urges the forward part of the pressure foot sole upwardly, alocking element pivotally mounted on said carrier and having a lowerportion projecting into the path of the rear portion of said sole, saidsole having bar means at the rear end thereof adapted to cooperate withsaid locking element, said locking element haivng stop surfaces which,in a first position thereof, cooperate with said bar means to limit thepivotal movement of said sole about its axle, second spring meansmounted on said carrier and normally urging said locking element towardits fiRst position, said stop surfaces of said locking element includingin addition a notched surface which, when said locking element is in asecond position thereof, when said presser foot is raised at thebeginning of a sewing operation, interlocks said locking element withthe bar means and cooperates with the first and second spring means tohold the sole substantially parallel to the needle plate as material tobe sewed is introduced into the machine and to be released from said barwhen said material to be sewed is transported beyond the pivoting axleof the sole by the material feed means.
 2. The material pressure foot asclaimed in claim 1, comprising lifting means adapted to lift the carrierand pressure foot sole, said locking element having a portion extendingabove the pivotal mounting on said carrier, said portion ending in aslanting surface, stationary means positioned in the path of saidslanting surface whereby upon lifting the carrier and pressure foot thelocking element is moved against the action of the second spring to itssecond position to lock the sole in its intermediate position.
 3. Thematerial pressure foot as claimed in claim 1 in combination with amaterial feed means constructed so as to cooperate with the materialpressure sole, said material feed means comprising a relatively longforwarding rod extending under the stitch plate, the material feeddevice having teeth for engaging the material being sewed being carriedby the forwarding rod, a slide motion translating shaft linked to oneend of the forwarding rod to impart a horizontal oscillating movement tothe forwarding rod and its material feed device, the other end of saidforwarding rod being linked to a vibratory lift shaft, said materialfeed rod and shafts being so constructed that the path of the teeth ofthe material feed move substantially parallel to the stitch plate whenextending through the slot in said stitch plate.